1. Field of the Invention
The invention relates to a photosensitive resin composition for a color filter of a liquid crystal display device; particularly, to a photosensitive resin composition for a color filter having a high development speed and good compatibility.
2. Description of the Related Art
Recently, a color filter has been applied widely in a color liquid crystal display device, color fax machine, color camera and other office equipments in the field. With the ever expanding market demand, the production technology of the color filter also tends to diversify. A dyeing method, a printing method, a plating method, and a dispersion method for the production have been developed, and wherein the dispersion method is a mainstream method.
In the dispersion method, a coloring pigment is first dispersed in a photosensitive resin, and then the photosensitive resin is coated on a glass substrate. After the steps of exposure and development, a specific pattern can be obtained. Such process is repeated three times, and a red (R), green (G) and blue (B) pattern of a colored pixel layer can be prepared thereby. Thereafter, a protective film is applied onto the pattern of the colored pixel layer as needed.
A photosensitive resin used in the dispersion method is as disclosed by Japanese Patent Publication Nos. 6-95211 and 8-183819. For example, a copolymer polymerized by (meth)acrylic acid monomer is applied as the photosensitive resin of an alkali-soluble resin.
However, the manufacturing process of the color filter comprises multiple heat treatment steps, such as a post-bake step after forming the red (R), green (G) and blue (B) pattern of the colored pixel layer, and a forming step of a transparent conductive film (ITO film). Such steps are generally operated at a high temperature of above 200° C. However, if the above mentioned conventional photosensitive resin is heated at 180° C. for about 1 hour, agglomerates of the pigment easily occur in the colored pixel layer (the particle sizes of the agglomerates of the pigment usually ranging from 1 to 10 μm), and the heat resistance of the colored pixel layer is also poor.
In order to resolve the above problems, Japanese Patent Publication No. 2010-145437 discloses a photosensitive resin composition comprising a polysiloxane as the alkali-soluble resin of the photosensitive resin. However, if using the polysiloxane as the alkali-soluble resin solely, the development property is not satisfactory.
In another aspect, Japanese Patent Publication No. 2012-027480 discloses a photosensitive resin composition, and a polysiloxane and an acrylic-based polymer are applied together to improve the adhesion between the photosensitive resin composition and the substrate, but the poor development property persists. Moreover, the poor compatibility between the resins is easily observed, and a satisfactory product is still absent.
Therefore, improving the development property and compatibility at the same time to meet the modern requirements is a target remained to be achieved in the technical field of the present invention.